Liquid crystal displays (“LCDs”) are being aggressively integrated into a multitude of contemporary electronic devices that previously employed cathode ray tubes (CRTs). “Liquid crystal” is a term that indicates the status of a substance that is neither solid nor liquid. When coming into contact with a grooved surface in a fixed direction, liquid crystal molecules line up in parallel along the grooves. Light travels through the spacing of the molecular arrangement. As the molecule arrangement is twisted, the light also “twists” as it passes through the liquid crystals. When a voltage is applied to the liquid crystal structure, the molecules rearrange themselves and the twisted light passes straight through. When voltage is applied to a combination of two polarizing filters and twisted liquid crystal, it becomes an LCD display. This is the principle behind conventional twisted nematic (TN) LCDs.
It is desirable to exploit the unique advantages of LCD displays, such as their compact size, thin profile, lightweight, low power consumption and ability to withstand elevated temperatures and vibrations, to produce items that are more compact and lightweight than CRTs. This means that LCDs can be used in many applications where a large CRT monitor does not fit or is impractical. Such products include LCD TVs, view cams, portable information tools (i.e. PDAs), computer monitors, A/V equipment, car navigation systems, game devices, large projection TVs and similar products. LCDs also deliver comparable performance in the display of color, resolution and brightness and further obviate the emission of harmful radiation attributable to emission by CRT monitors.
The typical LCD module includes a liquid crystal matrix mounted in or to a substrate that includes a plurality of discrete conductive regions disposed thereon. A liquid crystal cell is acquired by forming the requisite electrodes and then forming an alignment layer within which liquid crystal particles align themselves. Upper and lower glass substrates are thereafter coupled to one another and plastic beads are sandwiched therebetween. The substrates are then fixed, after which liquid crystals are injected into spaces between the plastic beads. Sealing of the LCD module is completed when external electronic elements, along with a driver, are connected to the electrodes of the finished cell.
Elastomeric connectors effect the most common method of connection of LCD modules to the conductive portion of a printed wiring board (PWB) or printed circuit board (PCB). Such connectors are generally silicone rubber strips made up of sequentially spaced conductive and non-conductive materials. Typical elastomeric connectors have at least one row of alternating layers of conductive and insulative compressible material that may be surrounded on its sides by a rubber supporting layer. The elastomeric connector is used in assemblies by mechanically confining the connector sides and compressing the connector through its height, thereby pressing the conductive elements in the connector onto conductive pads on the PWB and corresponding conductive pads on the LCD.
Increasing use of LCDs in delicate and complex electronic devices, however, increases the number of applications in which numerous interconnections must be made between the LCD and the PWB. Since there is limited space for these connections, it is imperative that the LCD pads and the PWB pads be tightly aligned over one another and that there be minimal angular skew in the conductive elements in the elastomer. This angle therefore becomes particularly important as the height of the connector increases. Absent such precise configuration, the conductors in the connector might not connect to the appropriate corresponding pads on the LCD and the PWB. In addition, since the connector is made from a rubbery material that is susceptible to movement under elevated temperature and vibrations, the retention of the elastomeric connectors to the PCB is minimal.
It is therefore desirable to provide an LCD surface mount connector that overcomes the problems inherent in elastomeric connectors. Particularly, it is desirable to provide such a connector that predictably and reliably retains conductive elements in precise alignment with one another.